1. Field of the Invention
The invention relates to a keyswitch structure, and especially relates to a keyswitch structure having a balance link and a balance link for a keyswitch structure.
2. Description of the Prior Art
The structure of conventional mechanical keyswitches is a keycap and a base plate with a lift mechanism therebetween such that the keycap is capable of moving up and down relative to the base plate. The movement stability, including movement stroke and even steadiness, of the keycap usually depends on the lift mechanism. If the movement of the lift mechanism itself is poor, the keycap can hardly move stably. Furthermore, if the length of the keycap such as space key is longer, a single lift mechanism cannot provide enough balance resilient force to the keycap leading to a slant easily when the keycap is pressed. Hence, in practice, the keycap with a longer length is usually provided with a plurality of lift mechanisms so that the resilient force produced after pressing the keycap is more balanced. However, in principle, each lift mechanism acts independently. Only by the structural constraint on one another through the keycap, the keycap still may slant after pressed in practice. For this problem, a common solution is using a balance link. The balance link is disposed independent of the lift mechanisms of the keyswitch structure. The balance link is provided in an n-shaped profile. The two ends thereof are movably connected to the base plate of the keyswitch structure; the middle portion thereof is rotatably connected to the bottom surface of the keycap of the keyswitch structure. Thereby, the balance link can constrain the up-and-down movement of the keycap to improve the movement stability. In general, for more constraint on the keycap by the balance link, the connection portion of the middle portion of the balance link with the keycap is as long as possible. In practice, the length of the middle portion is at least 70% of the length of the keycap. Because of the structural feature and the disposition of the lift mechanism and other components such as elastic domes (used for providing resilient force and triggering a switch) at the central portion of the keycap, the middle portion of the balance link cannot be disposed to pass through the central portion of the keycap. Hence, the middle portion of the balance link can be disposed only at a side portion of the keycap, so that the single balance link only constrains the keycap by a single side, which hardly provides effective constraint on the movement of the keycap. Furthermore, the conventional balance links are usually formed by bending flexible material. After several bending processes, the dimensions of the conventional balance link are easily out of precise control.